Maintaining accurate alignment between the frame and sashes of a window is a major factor in providing a good seal against wind and water between the sashes and the frame, as well as ensuring smooth operation of slidable sashes. Alignment of the window unit sashes, frame, and other members relative to one another is best done during factory assembly of the window unit. However, it has proven difficult, and often economically unfeasible, to maintain proper alignment of the unit during transport and possibly warehousing and retail display of the window units, without taking special, possibly expensive and inconvenient measures. Similar considerations also apply to sliding doors and gliding windows.
Misalignment can take several forms. Jambs may become warped or bent outwards, due, for example, to the outward pressure of seals and weather stripping between the sashes and the jambs. Window units may be improperly stacked at some point in the transportation process, allowing the weight of the sashes to cause excessive compression of the seals or weather stripping, to the point of creep, thereby causing poor sealing when the sashes are returned to their proper position. Various bumping and dropping of the window units may cause the corner angles of frames to deviate significantly from their intended values, typically 90°, a phenomenon known as racking.
While robust packaging can improve the chances of window units arriving at the construction site in an aligned condition, such packaging can become expensive, and there is still the possibility that misalignment will occur after removal of the packaging, but prior to installation.
There is therefore a need to preserve the alignment of sliding closures such as windows provided at the factory throughout the transportation, sale, and installation, without adding excessive cost and without complicating the installation process.